The present invention relates to synthetic elevation aperture processing. In particular, synthetic elevation aperture processes may provide increased resolution.
A volume is scanned acoustically for three-dimensional representations. The scan is performed with any of various arrays, such as one-dimensional, multi-row, or two-dimensional arrays. High resolution beamforming is typically provided in azimuth dimension. The linear one-dimensional array allows beamforming in a plane orthogonal to the array surface and passing through the center of every element. In the elevation dimension or orthogonal to the imaging plane, the resolution is affected by the amount of elevation focusing. One-dimensional arrays use a fixed mechanical focus in the elevation dimension. Curved elements along an elevation dimension may increase the elevation focus. A lens or other structure may also be used to provide a fixed focal length in the elevational dimension. A different elevation beamwidth is provided for different depths, such as a narrowest beamwidth at a focal point, a widest beamwidth at the deepest depth for imaging or scanning, and an elevation beamwidth equal to the elevation aperture width at the surface of the array.
For scanning a volume, the one-dimensional array is translated or rotated to sequentially scan different planes within the volume. For example, the array is rotated about a normal vector at the center of the array aperture. In the direction of rotation or a generally elevation direction, poor resolution may be provided due to the wide point spread function or elevation beamwidth close to the array and at the deeper depths for imaging. Since beamformation is provided within the imaging plane or along a radius of the scanned conical volume, high resolution is provided in the radial direction parallel to the array surface. Similarly for other rotations, such as associated with a wobbler transducer, or translations, the resolution along an elevation dimension may be poor relative to the resolution provided by beamforming within the imaging planes.